Trying to work meatless meals into your routine? A pot of hearty, healthy Cuban Black Beans makes a satisfying dish -- and enough leftovers for this recipe.
In a medium nonstick skillet, heat 1 teaspoon oil over medium. Add red onion and cook 1 minute. Add sugar and cook until dissolved. Add vinegar and season with salt and pepper. Transfer onion mixture to a small bowl and wipe out skillet. In a large bowl, mash 2 1/2 cups beans. Stir in bell pepper, cilantro, breadcrumbs, egg, and 1 1/2 cups beans. Season with 1/2 teaspoon salt and 1/4 teaspoon pepper and form mixture into 4 patties. Heat 1 tablespoon oil over medium-high. Cook 2 patties until crisp on outside and heated through, about 5 minutes, flipping once. Repeat with more oil and remaining patties. Spread mayonnaise on rolls; top with burgers, avocado, and onion mixture.